The present invention is related to the use of expansion chambers or expansion chambers and resonators to reduce electric motor fan noise.
Large electric motors are commonly cooled with in-line fans which draw or blow cooling air across the rotor and through the stator windings. At high speed, these fans can produce significant levels of noise. The noise is typically broad-band in character due to flow turbulence with embedded tones from the fan blade passage.
In transit car applications, the traction motors can develop undesirable levels of noise which are particularly noticeable since wheel and rail noises have been significantly reduce in modern cars due to the use of welded rails and rubber damped wheels.
Reactive silencers using tuned ports, resonators, and expansion chambers are the basis for designing mufflers on internal combustion engines.
It is an object of the present invention to provide electric motors with reduced noise levels at all operating speeds.